1. Field of the Invention
The present invention relates to an image forming apparatus, a method for controlling the image forming apparatus, and a storage medium.
2. Description of the Related Art
There is a conventional image forming apparatus that can operate in a tab slip sheet mode, according to which tab-attached sheets are inserted at predetermined positions of an output bundle that is composed of a plurality of sheets having an ordinary size, thereby generating an output document with heading and/or chapter tabs. For example, the tab-attached sheets to be used in this mode can be assembled as one set of a predetermined number of sheets. For example, five tab-attached sheets are one set of five sheets.
Further, another conventional image forming apparatus can operate in a slip sheet mode, according to which preprint sheets (i.e., sheets on which printing has been completed beforehand) are inserted as slip sheets, in addition to a front cover insertion mode. One set of a plurality of preprint sheets can be used in a case where the preprint sheets are inserted as slip sheets, similar to the above-described insertion of the tab-attached sheets. For example, preprint sheets on which chapter numbers are printed beforehand are one set of a plurality of sheets.
In the above-described image forming apparatuses, in a case where one set of a plurality of insertion sheets are inserted, if any one of the insertion sheets is disordered, all of a great amount of output products may be uselessly output. Hence, to confirm any disorder of the insertion sheets to be inserted, a conventional technique discussed in Japanese Patent Application Laid-Open No. 2007-171287 uses a sensor capable of reading a mark printed at a predetermined position of each insertion sheet to be inserted.
Further, a conventional technique discussed in Japanese Patent Application Laid-Open No. 2005-238817 includes reading an image of a predetermined insertion sheet beforehand, reading an image of an insertion sheet at insertion timing of the insertion sheet, and collating the image of the insertion sheet actually inserted with the image registered beforehand.
However, the above-described method discussed in Japanese Patent Application Laid-Open No. 2007-171287 includes performing preliminary printing of the above-described mark at the predetermined position. The print of the mark remains uselessly on an output product. Further, a printer equipped with a special sensor capable of reading the above-described mark is to be used. Further, the image forming apparatus capable of recognizing a sensor reading position and the shape of a mark is used when the printing is performed. Further, the method discussed in Japanese Patent Application Laid-Open No. 2005-238817 includes acquiring all images beforehand and, as a result, increases user's labor in a printing environment in which a great amount of pages are processed. In this respect, the method discussed in Japanese Patent Application Laid-Open No. 2005-238817 is not efficient.